The Solar System

Moons

How many moons does Mars have?

Mars has two moons, Phobos and Deimos. They were discovered in 1877 by the American astronomer Asaph Hall (1829–1907).

Mars’ two moons are Phobos (top), which has a radius of about 6.9 miles (11.1 kilometers); and Deimos, below, has an even smaller radius of 3.9 miles (6.2 kilometers). (Jet Propulsion Lab/California Institute of Technology—taken by Mars Reconnaissance Orbiter)